Hi Guys, I had a query regarding the DQS lines in DDR-SDRAM. As we know, most 16 bit wide DDR-SDRAM's provide 2 separate DQS (Data Strobe) lines for strobing the higher and the lower bytes respectively and these are I/O lines( is an input to SDRAM for writes to it and is an output from SDRAM for reads from it) . We are designing a DDR-SDRAM controller for 16-bit wide memories but due to shortage of pins want to provide only one DQS line from the controller for strobing these 16-bits of Data. For this we want to short both the LDQS and UDQS on the DDR-SDRAM side. When this signal is an input to the SDRAM, there is no problem but when the SDRAM is driving out the Data (for reads from SDRAM), both these lines will be asserted. Also the datasheet says that there could be a maximum skew of 500ps between the LDQS and UDQS. My concern is whether this shorting of two actively driven outputs will any problems on the board and on the reliability of the device. It is ensured that these lines will be driving the same logic level at any point of time with a maximum skew of 500ps, which means there could be a short for 500ps(assuming UDQS is low and LDQS is high) during reads from SDRAM. Will there be any long term problems with this arrangement or is it mandatory to provide separate lines from the controller for this ?? Also can this problem be handled by providing resistors on these lines before the shorting so that it does not become a dead short. The pads of the DDR-SDRAM are of the type SSTL2, Class II and we want to operate at a clock of 166MHz ( data rate of 333MHz). Please comment. Thanks and Regards Raghavendra ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu